class SessionTimeoutManager {
    constructor() {
        this.config = {
            timeout: 1800, // default 30 min
            warning_time: 1500, // default 5 min before timeout
            check_interval: 60000, // 1 minute
            logout_url: '/auth/logout',
            keep_alive_url: '/session/ping-activity',
            check_url: '/session/check-timeout'
        };
        this.timers = {
            checkTimer: null,
            logoutTimer: null,
            warningTimer: null
        };
        this.modal = null;
        this.warningShown = false;
    }

    async init() {
        try {
            await this.fetchConfig();
            this.setupEventListeners();
            this.startPeriodicChecks();
            console.log('Session timeout manager initialized with config:', this.config);
        } catch (error) {
            console.warn('Session timeout using default config due to error:', error.message);
            this.setupEventListeners();
            this.startPeriodicChecks();
        }
    }

    async fetchConfig() {
        try {
            const response = await fetch('/session/get-timeout-config', {
                method: 'GET',
                headers: {
                    'Accept': 'application/json',
                    'X-Requested-With': 'XMLHttpRequest'
                },
                credentials: 'same-origin'
            });
            
            if (!response.ok) {
                throw new Error(`HTTP ${response.status}`);
            }
            
            const data = await response.json();
            if (data.success) {
                this.config = { ...this.config, ...data };
            }
        } catch (error) {
            console.warn('Failed to load timeout config, using defaults:', error.message);
        }
    }

    setupEventListeners() {
        // Reset timers on user activity
        const events = ['mousedown', 'keydown', 'scroll', 'touchstart', 'click', 'input'];
        events.forEach(event => {
            document.addEventListener(event, () => this.resetActivity(), { passive: true });
        });

        // Handle visibility change
        document.addEventListener('visibilitychange', () => {
            if (!document.hidden) {
                this.checkSessionStatus();
            }
        });
    }

    async resetActivity() {
        try {
            await fetch(this.config.keep_alive_url, {
                method: 'POST',
                headers: {
                    'X-Requested-With': 'XMLHttpRequest'
                },
                credentials: 'same-origin'
            });
            this.clearWarning();
        } catch (error) {
            console.warn('Activity reset failed:', error);
        }
    }

    startPeriodicChecks() {
        this.timers.checkTimer = setInterval(() => {
            this.checkSessionStatus();
        }, this.config.check_interval);
    }

    async checkSessionStatus() {
        try {
            const response = await fetch(this.config.check_url, {
                method: 'GET',
                headers: {
                    'X-Requested-With': 'XMLHttpRequest'
                },
                credentials: 'same-origin'
            });

            if (!response.ok) {
                throw new Error(`HTTP ${response.status}`);
            }

            const data = await response.json();
            
            switch (data.status) {
                case 'expired':
                    this.handleSessionExpired(data);
                    break;
                case 'warning':
                    this.handleSessionWarning(data);
                    break;
                case 'active':
                    this.handleSessionActive(data);
                    break;
            }
        } catch (error) {
            console.warn('Session status check failed:', error);
        }
    }

    handleSessionExpired(data) {
        this.clearWarning();
        clearInterval(this.timers.checkTimer);
        
        if (data.redirect) {
            // Show message before redirect
            alert(data.message || 'Your session has expired. Please log in again.');
            window.location.href = data.redirect;
        } else {
            window.location.href = this.config.logout_url;
        }
    }

    handleSessionWarning(data) {
        if (!this.warningShown) {
            this.showWarning(data.time_remaining);
        } else {
            this.updateWarning(data.time_remaining);
        }
    }

    handleSessionActive(data) {
        this.clearWarning();
    }

    showWarning(timeRemaining) {
        this.warningShown = true;
        this.createWarningModal(timeRemaining);
    }

    updateWarning(timeRemaining) {
        if (this.modal) {
            const countdownElement = this.modal.querySelector('.countdown');
            if (countdownElement) {
                countdownElement.textContent = Math.max(0, timeRemaining);
            }
        }
    }

    createWarningModal(timeRemaining) {
        this.hideWarning();
        
        this.modal = document.createElement('div');
        this.modal.className = 'session-timeout-modal';
        this.modal.style.cssText = `
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0,0,0,0.8);
            z-index: 99999;
            display: flex;
            justify-content: center;
            align-items: center;
            font-family: Arial, sans-serif;
        `;
        
        this.modal.innerHTML = `
            <div style="background: white; padding: 30px; border-radius: 10px; text-align: center; max-width: 400px; box-shadow: 0 5px 25px rgba(0,0,0,0.3);">
                <h3 style="color: #d35400; margin-bottom: 20px; font-size: 1.5em;">Session About to Expire</h3>
                <p style="font-size: 1.1em; margin-bottom: 20px;">
                    Your session will expire in <span class="countdown" style="font-weight: bold; color: #e74c3c;">${timeRemaining}</span> seconds due to inactivity.
                </p>
                <div style="margin-top: 25px;">
                    <button onclick="sessionTimeout.continueSession()" 
                            style="background: #27ae60; color: white; border: none; padding: 12px 24px; 
                                   border-radius: 5px; cursor: pointer; margin-right: 15px; font-size: 1em;">
                        Continue Session
                    </button>
                    <button onclick="sessionTimeout.logout()" 
                            style="background: #e74c3c; color: white; border: none; padding: 12px 24px; 
                                   border-radius: 5px; cursor: pointer; font-size: 1em;">
                        Logout Now
                    </button>
                </div>
            </div>
        `;
        
        document.body.appendChild(this.modal);
        document.body.style.overflow = 'hidden';
    }

    hideWarning() {
        if (this.modal) {
            this.modal.remove();
            this.modal = null;
        }
        this.warningShown = false;
        document.body.style.overflow = '';
    }

    clearWarning() {
        this.hideWarning();
    }

    continueSession() {
        this.resetActivity();
        this.hideWarning();
    }

    logout() {
        window.location.href = this.config.logout_url;
    }

    destroy() {
        clearInterval(this.timers.checkTimer);
        this.hideWarning();
    }
}

// Initialize globally
const sessionTimeout = new SessionTimeoutManager();

// Start when DOM is ready
if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', () => sessionTimeout.init());
} else {
    sessionTimeout.init();
}

// Make available globally
window.sessionTimeout = sessionTimeout;